Stratified charge spark ignition internal combustion engine with exhaust recycle

ABSTRACT

A spark ignition system and a method for operating same by passing a first fuel-air mixture into a precombustion chamber of the engine and a second leaner fuel-air mixture into a primary combustion chamber, igniting the first mixture for igniting the second mixture, and controllably mixing about 5 to about 20 percent of the exhaust gas resulting from the combustion of the fuel mixtures with the second fuel-air mixture during operation of the engine at greater than about 75 percent maximum power output with the amount of exhaust gas being mixed with the second fuel-air mixture varying directly with the power output of the engine.

United States Patent 91 Alquist 5] May 7, 1974 I STRATIFIED CHARGE SPARKIGNITION INTERNAL COMBUSTION ENGINE WITH EXHAUST RECYCLE Henry E.Alquist, Bartlesville, Okla.

Phillips Petroleum Company, Bartlesville, Okla.

Filed: Sept. 25, 1972 Appl. No.: 291,612

Inventor:

Assignee:

References Cited UNITED STATES PATENTS 6/1947 Bicknell l23/ll9 A l2/l962May et a]. 123/75 B X I l/l969 Fryer et al 123/75 B INTAKE AIR AIRCLEANER I FOREIGN PATENTS OR APPLICATIONS 549,164 11/1957 Canada 123/119A Primary Examiner-Wendell E. Burns [5 7] ABSTRACT A spark ignitionsystem and a method for operating same by passing a first fuel-airmixture into a precombustion chamber of the engine and a second leanerfuel-air mixture into a primary combustion chamber, igniting the firstmixture'for igniting the second mixture, and controllably mixing about 5to about 20 percent of the exhaust gas resulting from the combustion ofthe fuel mixtures with the second fuel-air mixture during operation ofthe engine at greater than about 75 percent maximum power output withthe amount of exhaust gas being mixed with the second fuel-air mixturevarying directly with the power output of the engine.

9 Claims, 9 Drawing Figures EXHAUST RECIRCULATION CONTROL VALVE-SENSESINTAKE MANIFOLD PRESSURE IO ma i 2o EXHAUST RECIRCULATION 15 LINE ENGINEPATENTEUIAY 7 I974 sum 1 0r 5 INTAKE AIR AIR CLEANER I 10 FUEL-IiEXHAUST RECIRCULATION CONTROL VALVE-SENSES INTAKE MANIFOLD PRESSURE 2oEXHAUST RECIRCULATION 1 IJNE 6 I ENGINE F/G. I

EXHAUST VALVE INTAKE VALVE ARRANGEMENT 0F PRE AND MAIN CHAMBERS (TOPVIEW FIG. 2

PATENT EB In 1 1914 SHEET 2 0F 5 PDO mmF UDJA vE n m minnow 71914 SHEET3 Of OVERALL STOICHIOMETRIC FUEL 3 2mm m tmm v mmE $335 .6 Mb; 025

FIG. 3

UEnE

STOICHIOMETRIC FUEL OVERALL LEGEND 1000 RPM 7.0 COMP. RATIOO-CONVENTIONAL THROTTLE U-PRECHAMBER A-PRECHAMBER WITH 8 /o EGR MAX.POWER SPARK F MIXTURE TEMP. F COOLANT PATENTEOHAY 1 5974 3.809039 SHEETF o I v 40 s0 s0 70 a0 90 100 110 120 OVERALL sT0|cH|0METR|c FUEL 40 e0s0 ovERALL STOICHIOMETRIC FUEL.

1000 RPM LEGEND 7.0 COMP. RATIO O-CONVENTIONAL 8.0 THROTTLE U-PRECHAMBERMAX. PowER SPARK A-PRECHAMBER WITH 8 EGR F MIXTURE TEMP. F COOLANT FIG.5

PATENTED 71974 3.809.039

SHEET S U? I O I I Q I s" 0 I OVERALL /o STOICHIOMETRIC FUEL FIG. 7

E 3000 O. n.

40 50 6O 7O 8O 90 100 110 120 OVERALL "A; STOICHIOMETRIC FUEL 1000 RPMLEGEND 7.0 COMP. RATIO so THROTTLE MAX. POWER SPARK F MIXTURE F COOLANTO-CONVENTIONAL O-CONVENTIONAL WITH 7.4 V0 EGR UPRECHAMBER T'A-PRECHAMBER WITH 8.0 /o E-GR STRATIFIED CHARGE SPARK IGNITION INTERNALCOMBUSTION ENGINE WITH EXHAUST RECYCLE It is desirable to provide aspark ignition system which will operate with low pollution emissionswhile maintaining high power output and efiiciency.

This invention therefore resides in a spark ignition system and a methodof operating same by passing a first fuel-air mixture into aprecombustion chamber of the engine and a second leaner fuel-air mixtureinto a primary combusiton chamber, igniting the first mixture forigniting the second mixture, and controllably mixing about to about 20percent of the exhaust gas resulting from the combustion of the fuelmixtures with the second fuel-air mixture during operation of the engineat greater than about 75 percent maximum power output with the amount ofexhaust gas being mixed with the second fuel-air mixture varyingdirectly with the power output of the engine.

Other aspects, objects, and advantages of the present invention willbecome apparent from a study of the disclosure, the appended claims, andthe drawings.

The drawings are diagrammatic views of the apparatus and data of testsperformed on the apparatus. FIG. 1 shows the apparatus of thisinvention, FIG. 2 shows the combustion chambers, FIG. 2a shows element 6in more detail and FIGS. 3-8 show data of tests performed on the engine.

Referring to FIGS. 1 and 2, a spark ignition engine 2 has a primarycombustion zone 4 and a precombustion zone 6 that are in fluidcommunication one with the other. For simplicity, reference will be madeto the primary and precombustion zones in the singular. It should beunderstood, however, that the engine can have a plurality of primarycombustion zones, preferably with each primary zone having aprecombustion zone with the associated elements as set forth withreference to the singular zones.

Each of the combustion zones 4, 6 has a separate carburetor 8, connectedin fluid communication therewith which in turn is connected to an airsupply, afuel supply, and a throttle for controllably dischargingfuelair mixtures from the carburetors 8, 10 into their respectivecombustion zones 4, 6.

The carburetor 8 of the primary combustion zone or chamber 4 isconstructed to receive and mix fuel and air therein and discharge afuel-air mixture into the primary combustion zone 4 that is a relativelylean fuel-air mixture, being less than about an 80 percentstoichiometric fuel.

The carburetor 10 of the precombustion zone or chamber 6 is constructedto receive and mix fuel and air therein and discharge a fuel-air mixtureinto the pre-' combustion chamber 4 that is a richer mixture relative tothe other fuel mixture, preferably a fuel-air mixture in the range ofabout a 500 to about a 1,000 percent stoichiometric fuel.

A spark ignition system, generally referred to by numeral 12, isassociated with the precombustion chamber 6 for igniting the fuelairmixture therein, which in turn ignites the fuel-air mixture in theprimary combustion zone 4 for operating the engine 2.

An exhaust conduit 14 (FIG. 1) is connected to the exhaust outlet of theprimary combustion chamber 4 for directing the exhaust gas resultingfrom combustion of the first and second fuel-air mixtures from theengine 2.

An exhaust gas recirculating conduit 16 is connected in fluidcommunication with the primary combustion zone 4 and the exhaust conduit14.

A measuring means, for example a pressure controller 18, is associatedwith the engine 2 for measuring a variable representative of the poweroutput of the engine 2 and delivering a signal representative thereof.For example, the measuring means can measure the intake manifoldpressure of the primary combustion zone 4 as shown in FIG. 1.

A control means, such as a control valve 20 for example, is positionedin the exhaust gas recirculating conduit l6 and is connected to themeasuring means 18 for receiving a signal therefrom and opening andclosing the valve in response to said signal. The valve 20 isconstructed to be in the closed position in response to a signalrepresentative of the output of the engine being less than about percentmaximum power output of the engine. The valve 20 is open andcontrollably positioned in response to a signal from the measuring meansrepresentative of the output of the engine 2 being greater than about 75percent maximum power output with the opening of said valve 20 varyingdirectly with the power output of the engine 2 and passing exhaust gasin the range of about 5 to about 20 percent of the total exhaust gaspassing through conduit 14.

FIGS. 3-8 show the results of tests on an engine of this invention.

The precombustion chamber used in these tests had the followingcharacteristics:

Shape: cylindrical Orifice: one-eighth in. square edge Volume: 0.83 cu.in.

Intake valve location: rear of chamber Spark gap location: rear ofchamber Length/Diameter: 3.80

The precombustion chamber was operated with a supply of fuel-air mixturesuch that 88 percent of the precombustion chamber volume was filled withmixmm at the beginning of the compression stroke. Fuel was present inthe mixture supplied the precombustion chamber in an amount 5 times thatrequired for a stoichiometric mixture, i.e., 500 percent stoichiometricfuel.

The engine used was a CFR, single cylinder unit similar in basicconfiguration to the standard knock-test engine except for twoadditional combustion chamber access holes. A sketch of the arrangementof the precombustion chamber and the main CFR engine combustion chamberis shown in FIG. 2. The fuel was a conventional premium grade gasolinehaving a research octane number of 99 and containing 2.5 ml TEL pergallon.

Inlieu of an acceptable technique for the direct measurement of noise,the effect of exhaust gas recirculation (EGR) to reduce noise wasdocumented in terms of the peak value of the first time-derivative ofcylinder pressure. The filtered output of the standard D-l,magnetostrictive knock-test pickup furnished the dP/dT signal. FIG. 3presents peak dP/dT values on an arbitrary, but linear, scale asfunctions of stoichiometry. Results of the conventional engine, theprecombustion chambered engine, and the precombustion chambered enginewith 8 percent EGR are included. Objectionable combustion noise did notoccur below a value of 6 on the scale in FIG. 3. Thus, the data in thatFigure showed that 8 percent EGR in the precombustion chambered engineextended noise-limited operation to 1. A method for operating a sparkignition engine having a precombustion chamber in communication with aprimary combustion zone and means for igniting a fuel-air mixture in theprecombustion chamber, com- 103 percent stoichiometric fuel from 89percent with 5 prising: a

no EGR. This is judged to be a significant expansion of the usefuloperation range of the precombustion chambered engine.

FIG. 4 presents exhaust NO, concentrations (as NO) plotted against thepercentage stoichiometric fuel. At all stoichiometries richer than 70percent stoichiometric fuel, 8 percent EGR reduced NO; emission. Atstoichiometrics leaner than 70 percent, the presence of recirculatedexhaust gas appeared to increase NO,,. Although the reasons for thisincrease are unknown, it is unimportant since NO; values with theprechambered engine were quite low at the stoichiometries where theincrease occurred. Hence, there would be no incentive for EGRapplication in this stoichiometry range. Eight Percent EGR reduced Nfrom the precombustion. chambered engine about 54 percent at 90 percentstoichiometric fuel at constant power.

FIG. 5 shows that 8 percent EGR in the precombustion chambered engineproduced a 4 to 7 percent loss of power at constant throttle. Theprechambered engine without EGR resulted in a 5 to 9 percent decrease inpower as compared to the conventional engine. The total power decreaseattributed to the simultaneous application of the precombustionchambered combustion process and the 8 percent EGR' was about 12percent. Although not desirable, this power loss is certainlyacceptable.

FIG. 6 shows that 8 percent EGR had only a mirror effect on exhausthydrocarbon concentrations. From I00 percent to 70 percentstoichiometric fuel, which is the range where EGR is applied to theprecombustion chambered engine, 8 percent EGR increased hydrocarbonemissions no more than 14 percent and as little as 6 percent.

FIG. 7 shows that the influence of 8 percent EGR on the carbon monoxideemissions from a precombustion chambered engine is negligible.

FIG. 8 compares the effectiveness of about the same amount of exhaustgas recirculation (EGR) on NO formation from a conventional engine and aprechambered engine. This figure shows that applying EGR to theprechambered engine has about the same benefit on NO (at a givenstoichiometric mixture) as the application of EGR to the conventionalengine. However, with the conventional engine, the application of EGRenrichens the lean misfire limit from about 74 percent stoichiometricfuel to about 89 percent stoichiometric fuel (see FIG. 8) which limitsthe usefulness of EGR. With the prechambered engine, the application ofEGR has no deleterious effect on lean misfire limit. In addition, EGRhas the other important benefit of substantially reducing excessiverates of pressure rise (leading -to noise) of the prechambered engine.

This invention therefore provides a spark ignition engine which willoperate with low pollution emissions while maintaining high power outputand efficiency.

Other modifications and alterations of this invention 7 will becomeapparent to those skilled in the art from controllably passing a firstfuel-air mixture into the precombustion chamber;

controllably passing a second fuel-air mixture into the primarycombustion zone, said second fuel-air mixture being a leaner fuelmixture relative to the first mixture; I I

igniting the first mixture in the precombustion zone for igniting thesecond mixture in the primary combustion zone; and

controllably mixing about 5 to about 20 percent of the exhaust gasresulting from the combustion of the first and second fuel-air mixtureswith the second fuel-air mixture during operation of the engine atgreater than about percent maximum power output of the engine, saidamount-of exhaust gas being mixed with the second fuel-air mixturevarying directly with the power output of the engine.

2. A method, as set forth in claim 1, wherein the first fuel-air mixtureis in the range of about a 500 to about a 1000 percent stoichiometricfuel.

3. A method, as set forth in claim 1, wherein the second fuel-airmixture is less than about an percent stoichiometric fuel.

4. A method, as set forth in claim 3, wherein the first fuel-air mixtureis in the range of about a 500 to about a 1,000 percent stoichiometricfuel.

5. In a spark ignition system having a primary combustion zone, mixingmeans for controllably mixing a primary fuel-air mixture, and means forpassing said primary fuel-air mixture into the primary combustion zone,the improvement comprising:

a precombustion chamber being in fluid communication with the primarycombustion zone;

mixing means for controllably mixing another fuel-air mixture being aricher fuel mixture relative to said primary fuel-air mixture;

meansfor passing said other fuel-air mixture into the precombustionchamber;

means for igniting the fuel-air mixture in the precombustion chamber forigniting the primary fuel-air mixture in the primary combustion zone;

exhaust means for directing the combustion gas resulting from combustionofthe fuel-air mixture from the engine;

measuring means for measuring a variable representative of the poweroutput of the engine and delivering a signal in response thereto;

a conduit connected in fluid communication with the exhaust means andthe primary combustion chamber;

control means for passing about 5 to about 20 percent of the exhaust gasresulting from the combustion of the first and second fuel-air mixturesinto the primary combustion chamber during operation of the engine atgreater than about 75 percent maximum power output of the engine, saidcontrol means comprising a control valve positioned in the conduit andconnected to the measuring means, said valve being in a closed positionin response to a signal from the measuring means representative of theoutput of the engine being less than about 75 percent maximum poweroutput and said valve being controllably opened in response to a signalfrom the measuring means representative of the output of the enginebeing greater than about 75 percent maximum power output with theopening of said valve varying directly with the power output 5 of theengine.

6. An apparatus, as set forth in claim 5, wherein the variable measuredby the measuring means is the manifold pressure of the primarycombustion zone.

7. An apparatus, as set forth in claim 5, wherein the mixing means forthe primary fuel-air mixture is a carburetor adapted to provide afuel-air mixture less than about an percent stoichiometric fuel.

1. A method for operating a spark ignition engine having a precombustionchamber in communication with a primary combustion zone and means forigniting a fuel-air mixture in the precombustion chamber, comprising:controllably passing a first fuel-air mixture into the precombustionchamber; controllably passing a second fuel-air mixture into the primarycombustion zone, said second fuel-air mixture being a leaner fuelmixture relative to the first mixture; igniting the first mixture in theprecombustion zone for igniting the second mixture in the primarycombustion zone; and controllably mixing about 5 to about 20 percent ofthe exhaust gas resulting from the combustion of the first and secondfuelair mixtures with the second fuel-air mixture during operation ofthe engine at greater than About 75 percent maximum power output of theengine, said amount of exhaust gas being mixed with the second fuel-airmixture varying directly with the power output of the engine.
 2. Amethod, as set forth in claim 1, wherein the first fuel-air mixture isin the range of about a 500 to about a 1000 percent stoichiometric fuel.3. A method, as set forth in claim 1, wherein the second fuel-airmixture is less than about an 80 percent stoichiometric fuel.
 4. Amethod, as set forth in claim 3, wherein the first fuel-air mixture isin the range of about a 500 to about a 1,000 percent stoichiometricfuel.
 5. In a spark ignition system having a primary combustion zone,mixing means for controllably mixing a primary fuel-air mixture, andmeans for passing said primary fuel-air mixture into the primarycombustion zone, the improvement comprising: a precombustion chamberbeing in fluid communication with the primary combustion zone; mixingmeans for controllably mixing another fuel-air mixture being a richerfuel mixture relative to said primary fuel-air mixture; means forpassing said other fuel-air mixture into the precombustion chamber;means for igniting the fuel-air mixture in the precombustion chamber forigniting the primary fuel-air mixture in the primary combustion zone;exhaust means for directing the combustion gas resulting from combustionof the fuel-air mixture from the engine; measuring means for measuring avariable representative of the power output of the engine and deliveringa signal in response thereto; a conduit connected in fluid communicationwith the exhaust means and the primary combustion chamber; control meansfor passing about 5 to about 20 percent of the exhaust gas resultingfrom the combustion of the first and second fuel-air mixtures into theprimary combustion chamber during operation of the engine at greaterthan about 75 percent maximum power output of the engine, said controlmeans comprising a control valve positioned in the conduit and connectedto the measuring means, said valve being in a closed position inresponse to a signal from the measuring means representative of theoutput of the engine being less than about 75 percent maximum poweroutput and said valve being controllably opened in response to a signalfrom the measuring means representative of the output of the enginebeing greater than about 75 percent maximum power output with theopening of said valve varying directly with the power output of theengine.
 6. An apparatus, as set forth in claim 5, wherein the variablemeasured by the measuring means is the manifold pressure of the primarycombustion zone.
 7. An apparatus, as set forth in claim 5, wherein themixing means for the primary fuel-air mixture is a carburetor adapted toprovide a fuel-air mixture less than about 80 percent stoichiometricfuel.
 8. An apparatus, as set forth in claim 5, wherein the mixing meansfor the other fuel-air mixture is a carburetor adapted to provide afuel-air mixture in the range of about a 500 to about a 1,000 percentstoichiometric fuel.
 9. An apparatus, as set forth in claim 8, whereinthe mixing means for the primary fuel-air mixture is a carburet0radapted to provide a fuel-air mixture less than about an 80 percentstoichiometric fuel.